Thermally Activated Delayed Fluorescence Sensitizers As Organic and Green Alternatives in Energy-Transfer Photocatalysis

Abstract

Photocatalysis has captured the imagination of synthetic chemists and is poised to become a staple of the fine chemical industry. Over the past decade, the subfield of energy-transfer (EnT) catalysis has expanded dramatically, harnessing the excited states of a photosensitizer to unlock a variety of redox-neutral, radical-based reactivities in a mild and selective fashion. However, many of the developments in this discipline rely on precious rare earth metals such as iridium. This perspective will highlight the rise of thermally activated delayed fluorescence (TADF) materials as metal-free alternatives in EnT photocatalysis for organic transformations. Emphasis will be placed on the recent progress of cycloadditions, E/Z isomerization of olefins, and other radical-initiated processes; all mediated by the mechanism of Dexter energy transfer. The tunable excited-state energetics and dynamics of TADF materials allow them to effectively compete with iridium-based sensitizers, indicating their promise as green alternatives in organocatalysis.